I think that depends very much on the person. It really does make sense that sharing with people who care about you would be beneficial, but it really doesn't seem to work for me. If I tell my goal even to someone who is close to me too early, I'm just much less likely to do it. It's as if a large chunk of that intrinsic motivation is just gone as soon as I verbalize my goal or plan to any sort of audience. It impacts me on a small as well as large scale.
Small scale example: If I tell my partner that I plan on going to the gym this weekend, I'm less likely to go when the time actually comes. If I make a plan to go to the gym but don't tell anyone, I'll probably do it.
Larger scale example: When I decided to try selling my fiction writing, I purposefully told no one for about two or three months, until I made some sales. Then, when I felt I had enough momentum and something to show for my plans, I told my partner what I've been doing. He was very very supportive. But then I fell into a habit of telling him _too much_ about my writing journey and plans, thinking it's safe now. It wasn't. The more I talked about it, the less I actually did it. It got to the point where I had to go into lockdown mode of not talking about it at all (and asking him not to ask). Now, I am careful to only talk to him about aspects of writing I've already finished. I can talk about how I've released a book, or what challenges I had in the last release. But I can't talk to him about what I'm writing this weekend, or what my plans are for my writing, or when I hope to have my next release.